Stereotypy, describing motor behavior that is repetitive, rhythmical, and non-goal directed, is commonly observed in persons with autism and other developmental disabilities. For some children with autism or other developmental disabilities, stereotypy may be a target for intervention. On the other hand, stereotypy may serve as a proxy for other behaviors or conditions, for example, anxiety or mood disorders that are targeted for treatment. Taken together, stereotypy is a long-recognized and important behavior for persons with developmental disabilities. Measurement difficulties present an obstacle to the study of stereotypy, and ultimately, to its treatment. The objective of this program is to provide a tool that quantifies the level of stereotypy in autistic children. This will be achieved through an innovative integration of triaxial accelerometer and radio frequency telemetry technologies. The resulting long-term, free-living measurements performed in the clinic and at the subject's home, will provide objective measures of clinical change in autism treatment. [unreadable] [unreadable]